Mate in 18

In a game of speed chess I mated my opponent in 18 moves. My opponent was Borosimic of Germany, who played black. Here are the moves of the game along with my commentary:

1. e4 g6
2. d4 Bg7
3. Nf3 e6
4. Be3 h6

I overprotect my d-pawn. Black has only one developed piece.

5. Nc3 Nc6
6. Bd3 a6

Black's move prevents me from moving a piece to b5, but it's better for black to develop a piece.

7. Qe2 b5

I can castle on either side.

8. a3 Bb7
9. 0-0 Nf6
10. Rad1 g5

Black decides not to castle.

11. d5 Ne7
12. dxe fxe

I want to deliver a check with my queen on h5, but to do so I must move the black knight from f6 and clear the diagonal for my queen.

13. e5 g4

I expect the black knight to move, but black counterattacks.

14. Nd4 Nfd5
15. Qxg4 Nxe3

Here I have the option of capturing the black knight, but I decide to check first to prevent castling.

16. Qh5+ Kf8
17. fxe3+ Kg8

I capture with check. Mate is now inevitable.

18. Qf7#

My bishop prevents the white king from escaping to h7. All of black's pieces are on his first and second ranks. Black plays aggressively, but his failure to protect his king leads to his defeat.